This invention relates to implantable medical devices (IMDs). In particular, the invention relates to the housing of an implantable medical device formed of a titanium alloy.
Implantable medical devices are used to produce therapeutic results in a patient and for monitoring physiologic parameters of a patient. Examples of IMDs include implantable drug infusion pumps, implantable neurostimulators, implantable cardioverter defibrillators, implantable cardiac pacemakers, and cochlear implants. Most of these IMDs either provide an electrical output or contain electrical circuitry to perform their intended functions. These devices are typically powered by a battery contained within the housing of the implantable medical device.
Since useful life of an IMD is dependent upon the operating life of the battery that provides power, the development of rechargeable power sources that can be charged using electromagnetic energy from outside the patient's body provides the opportunity for longer life IMDs. The ability to deliver electromagnetic energy to the charging circuitry within the IMD is affected by the electrical characteristics of the housing of the implantable medical device. Typically, implantable medical device housings are made of a biocompatible metal such as commercial pure (CP) titanium. To improve electrical performance of the recharging circuitry, a housing of a material having a higher resistivity than conventional CP titanium housings is desirable. A higher resistivity housing would also enhance telemetry to and from the IMD, and would reduce magnetic resonance imaging (MRI) heating effects when a patient with an IMD is subjected to an MRI procedure.